Field
The disclosure relates to a propulsion system for a missile. More particularly, applying at least a portion of ramjet impulse during the booster phase improves performance for short range missions.
Description of the Related Art
A ramjet missile requires a conventional rocket boost phase to reach high supersonic speeds, after which the ramjet can operate as designed. The specific impulse, or fuel consumption, of the ramjet phase is 3 to 4 times more efficient than the rocket phase, but the ramjet phase delivers a lower thrust level over an extended period. Because of this, at short launch ranges, the rocket is able to accelerate and intercept a target in less time than the boosted ramjet. For longer range intercepts, the ramjet is able to propel the missile much greater distances.
U.S. Pat. No. 8,056,319 B2, titled “Combined Cycle Missile Engine System,” is assigned to the same assignee as the present patent application. The patent discloses a ducted rocket, also called an air augmented rocket, using the airflow induced into the engine to produce more thrust (augmentation) than would be produced by the rocket alone. Augmentation is low until a flight speed of Mach 1.5 is exceeded. This is due to low ram pressure at low supersonic speeds. Above Mach 1.5, the augmentation rises rapidly and can be in excess of 100%, twice the rocket only thrust. The disclosure of U.S. Pat. No. 8,056,319 B2 is incorporated by reference herein in its entirety.